some expressions help?

Adobe After Effects Expressions

some expressions help?

Posted by Guy on May 6, 2005 at 8:38 pm

I’d have a random wiggle expression:

seedRandom(13,true);
wiggle(7,15)

but would like to get it to decay over time, have the action trail off (in a controllable way)
Perhaps using some decay code Dan Ebberts was kind enough to provide:

t = time;
if (t > 0){
freq =3;
amplitude = 50;
decay = 3.0;

s = amplitude*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);

value + [s,s]
}else{
value
}

The beauty of this decay is that I can tweak it by changing freq, amplitude, decay values.
I just don’t know how to put this all together.

thanks!

Guy replied 21 years ago 2 Members · 2 Replies
2 Replies

Dan Ebberts

May 6, 2005 at 8:50 pm

Something like this might be what you’re looking for:


initialAmp = 15;
decay = 3;
freq = 7;
decayStartTime = 2;

if (time < decayStartTime){
  amp = initialAmp;
}else{
  amp = initialAmp/Math.exp(decay*(time - decayStartTime));
} 

wiggle(freq,amp)

Dan

Guy
May 7, 2005 at 3:56 pm

exactly! Thanks again Dan.

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